Wastewater and Stormwater Systems in Buildings
Communal Bathroom Plumbing
In a communal bathroom, a siphon system can handle discharge from toilets and urinals. The drainage system should be reinforced, with a single trap for each fixture. Never install two devices with a shared trap, as this creates an air bubble preventing water from draining.
The siphon tube diameter connects to the stack, boat, and basin. The siphon pot connects to the sink with a 30mm or 50mm siphon.
Velocity Limits in Sanitation Channels
Why are there upper and lower speed limits?
- Lower limit: To prevent solids deposition at low speeds.
- Upper limit: To prevent pipe wall corrosion at high speeds.
Water Seals
Purpose and Types
Water seals prevent gaseous emissions from the drainage network from entering buildings while allowing wastewater and solids to pass. Types include:
- Individual traps (P and S types)
- Pot siphons
- Siphonic sumps
- Manholes
Wastewater Pumps
When are pumps necessary?
Pumps are needed when the final wastewater discharge point is below the sewage line’s altitude.
Unitary vs. Separate Sewerage Systems
Flow Differences
In a unitary system, flows are higher during wet weather (rain) than in dry weather. A unitary system handles both sewage and rainwater. In a separate system, wastewater and stormwater are collected independently.
Slope and Unit Load Loss
In a free-flowing drainage pipe, a steeper slope increases friction and unit load loss.
Solving Drainage Issues in Public Buildings
If multiple toilets and sinks on a long, small-diameter pipe drain slowly, ensure atmospheric pressure by installing a primary ventilation network connected to outside air.
Horizontal Drainage Consolidation
A very gentle slope in horizontal drainage can decrease the flow rate, causing solids to deposit and block the pipe.
Wastewater and Stormwater Disposal Systems
Systems include:
- Unitary system: Collects sewage and rainwater together.
- Separate systems: Collect wastewater and stormwater separately.
- Combined system: Collects water separately but discharges it into the same network.
Preventing Siphonage in Multi-Story Buildings
Toilet discharge can create overpressure and depression in the downspout, causing siphonage in upper-floor toilets. Solve this with tertiary ventilation between the hydraulic piston and lock, releasing pressure.
Understanding Siphonage
Siphonage (or auto-siphonage) occurs during fixture discharge, especially with long, narrow branch pipes or inadequate ventilation.
Siphon Bottle
Definition and Function
A siphon bottle connects medical devices to the drainage network, collecting discharged water and acting as a water seal.
Downspout
Definition
A downspout is a vertical pipe that evacuates rainwater and sewage to lower levels (ground floor or basement).
Types of Manholes
Manhole types in sewerage systems include:
- Downspout manholes
- Inspection chambers
- Pass-through manholes
- Siphon manholes
- Sump manholes
Sewer Venting Types
- Primary: Extends the stack above the roof, connecting to outside air.
- Secondary: A parallel column connected to the stack at the top and bottom (and potentially at intermediate floors), also venting above the roof.
- Tertiary: Horizontal network linking the secondary vent with individual fixture water seals.
Basic Sewer Requirements
Sewer systems should have:
- The simplest path, distances, and slopes for self-cleaning and waste evacuation.
- Appropriate pipe diameters for safe flow.
- Water seals to prevent air passage without affecting waste flow.
- Adequate ventilation for water seal function and gas extraction.
- Exclusive use for sewage and runoff (no other waste).
Pipeline Diameter Parameters
Diameter depends on the building’s discharge units and the square meters of terraces and patios.
Horizontal Network Installation
Horizontal networks can be:
- Suspended from the ceiling
- Cast into the floor
- Underground, beneath the lowest floor’s pavement